1. Filed of the Invention
The present invention relates to a method of producing a semiconductor device and a configuration thereof. More particularly, it relates to a method of producing a resin-sealed semiconductor device and a configuration thereof which make it possible to decrease the size, thickness, weight and cost of the device.
2. Description of the Related Art
FIGS. 10A and 10B show a gull-wing type semiconductor device with the configuration of the prior art, FIG. 10A being a cross sectional view thereof and FIG. 10B being a top view (perspective view) thereof.
A semiconductor device of this configuration is generally produced in such steps as shown in FIG. 11, in a procedure described below. A semiconductor element 3 is bonded by means of a die bonding material 2 on an island 14 of a lead frame 6 which has the islands 14 and leads 1 as shown in FIG. 12. Then after connecting an inner lead section la of the lead 1 surrounding the island 14 to an electrode pad located on the semiconductor element 3 by wire bonding of a wire 4 such as gold wire, the elements are sealed individually on both sides of the lead frame 6 by using a sealing resin 5. FIG. 13 is a top view of the semiconductor device with the configuration of the prior art after being sealed with the resin (the sealing resin is indicated with dotted line). In a last stage, an outer lead section 1b of the lead 1 is plated with tin or the like, cut off from the lead frame 6 and formed in gull wing shape, thereby to obtain the semiconductor device as in FIG. 12.
In the method of the prior art, it is necessary to prepare the lead frame 6 having the islands 14 matched to the size of the semiconductor elements 3 and molding dies (not shown) for sealing the individual semiconductor elements with resin. Therefore, when semiconductor elements 3 of different specifications are used, it is necessary to prepare different lead frames 6 and different molding dies for the various specifications.
In the semiconductor device of the prior art shown in FIG. 12, there has been a limitation on the reduction of the size and weight of the semiconductor device because the resin covers both sides of the lead frame 6.
Moreover, because heat generated by the semiconductor element 3 is dissipated through the lead 6, it is difficult to apply the device to power transistors which generate much heat and, because of the relatively long connection between the semiconductor element 3 and a mother board, it is also difficult to apply the device to high-frequency transistors or the like.
To counter such problems as described above, a molded transistor of chip on lead (COL) configuration wherein a semiconductor chip is directly connected on a lead is disclosed, for example, in Japanese Patent Kokai Publication No. 9-27584. However, since production of such a molded transistor requires different lead frames for different specifications and molding with the resin is carried out individually for each semiconductor element, different molding dies must be prepared for different specifications and therefore the above problems are not solved.
Also because the devices are mounted on the mother board by using outer leads, the technology is difficult to be applied to devices which generate much heat and high-frequency elements.
An object of the present invention to provide a method of producing the semiconductor device wherein semiconductor elements are sealed with resin by using the same lead and other means regardless of the specifications of the semiconductor elements, and a semiconductor device which can be reduced in size and weight and has good heat dissipation performance and high-frequency performance.
The present inventors have intensively studied. As a result, they found that semiconductor devices can be produced with a same lead frame regardless of the specifications of semiconductor elements when a plurality of the semiconductor elements are mounted on the lead frame having the leads disposed substantially parallel to each other and, after sealing the whole with a resin, the individual semiconductor devices are cut off, and that the semiconductor device produced with this method has improved heat dissipation performance and high-frequency performance. Thus, the present invention has been accomplished.
The invention provides a method of producing a semiconductor device comprising a die bond pad, a wire bond pad, a semiconductor element mounted on the die bond pad, and a sealing resin for molding the semiconductor elements, which comprises preparing a lead frame having a plurality of leads disposed substantially in parallel to each other at intervals in the longitudinal direction in the same plane; bonding a plurality of semiconductor elements in parallel on at least one lead surface of the lead frame; electrically connecting an electrode of each semiconductor element, the lead having the semiconductor element bonded thereon and another lead adjacent therewith in the longitudinal direction; molding the plurality of semiconductor elements together by means of the sealing resin applied from above the lead surface so that the back side of the lead is exposed; and cutting the leads in the longitudinal direction to divide the lead with the semiconductor element being bonded thereon into a portion where the semiconductor element is bonded thereon and a portion which is connected to the electrode, and to divide the other lead into portions connected to different electrodes, thereby to take the lead with the semiconductor element being bonded thereon as a die bond pad, and to take the lead connected to the electrode as a wire bond pad.
With this method of producing the semiconductor element, it becomes possible to produce the semiconductor device having semiconductor elements of different sizes mounted thereon by using the lead frame of the same configuration, and therefore the production process can be simplified and the production cost can be reduced.
Also with this method, because the lead frame whereon the semiconductor elements are bonded is sealed with the resin as a whole at the same time, it is not necessary to prepare different molding dies for resin sealing of semiconductor devices of different sizes as in the case of the prior art where the semiconductor devices are sealed with a resin individually, thus making it possible to reduce the production cost.
In mass production, because the semiconductor devices are made by cutting off the lead frame whereon the semiconductor elements are mounted consecutively as shown in FIG. 3A, there is no part of the lead frame to be wasted, so that product yield per unit area of the lead frame is improved and the production cost can be reduced.
Moreover, even when the size of the semiconductor element is changed, the semiconductor devices can be produced by using the same lead frame. Thus, it is not necessary to prepare lead frames having islands of different sizes for the semiconductor elements of different sizes as in the case of the prior art, thereby making it possible to reduce the production cost by using the common lead frame.
The present invention provides a method of producing a semiconductor device comprising a die bond pad, a wire bond pad, a semiconductor element mounted on the die bond pad, and a sealing resin for molding the semiconductor element, which comprises preparing a lead frame having comb-shaped leads which are symmetrically disposed substantially in parallel and opposite to each other at intervals in the longitudinal direction in the same plane; bonding semiconductor elements on every other leads among the leads arranged in the longitudinal direction on at least one side of the symmetrical arrangement; electrically connecting an electrode of the semiconductor element and another lead adjacent to the former lead; molding the semiconductor elements together by means of the sealing resin applied from above the lead surface so that the back side of the lead is exposed; and cutting the lead and the sealing resin in the longitudinal direction to separate from the lead frame, thereby to take the lead with the semiconductor element bonded thereon as a die bond pad, and to take the lead connected to the electrode as a wire bond pad.
A plurality of wire bond pads can be made similarly also by using the lead frame having the leads which are cut beforehand, as described above.
The semiconductor element may also be bonded across a plurality of the leads which are disposed in the longitudinal direction.
This method makes it possible to produce the semiconductor device by using the same lead frame even when size of the semiconductor element is changed, and therefore production cost can be reduced by using the common lead frame.
The semiconductor element may also be bonded across a plurality of the leads which are disposed in the lateral direction to oppose each other.
This method makes it possible to produce the semiconductor device by using the same lead frame even when size of the semiconductor element, the electrode position and/or other specifications are changed, and therefore production cost can be reduced by using the common lead frame.
The semiconductor element may also be bonded onto the lead surface by means of an electrically conductive or insulating bonding material.
When an electrically conductive resin is used, the semiconductor element and the lead below thereof can be electrically connected.
The present invention also provides a method of producing the semiconductor device, wherein the sealing resin is cut off in the lateral direction outside a plurality of the semiconductor elements so that the plurality of semiconductor elements arranged in the longitudinal direction are molded in the same sealing resin.
By employing this method, it becomes possible to produce the semiconductor device where the plurality of semiconductor elements are molded together in the sealing resin.
The number of the semiconductor elements sealed in the semiconductor device can be freely changed by changing the cutting position.
The present invention also provides a lead frame comprising a plurality of leads arranged substantially parallel to each other in the longitudinal direction at intervals in the same plane.
By supplying the leads in the form of the lead frame described above, handling of the leads is made easier.
The present invention also provides a lead frame having comb-shaped leads which are symmetrically disposed and opposing substantially in parallel to each other at intervals in the longitudinal direction in the same plane.
By using the lead frame of this configuration, it becomes unnecessary to provide a step of half-cutting the leads which have been sealed with resin.
The present invention also provides a semiconductor device comprising a die bond pad with a semiconductor element mounted on the top surface thereof, a wire bond pad arranged substantially in parallel to the die bond pads in the longitudinal direction and connected to electrodes of the semiconductor elements, and a sealing resin for molding the semiconductor element, wherein additional wire bond pads are disposed in parallel with the die bond pads and the wire bond pads, while the sealing resin is applied from above the die bond pads and the wire bond pads so that the back surfaces of the die bond pads and the wire bond pads are exposed.
In a semiconductor device of such a configuration as described above, only the top surface of the semiconductor device is sealed with the resin while the die bond pads and the wire bond pads formed by cutting off the leads are exposed on the back surface, and therefore it becomes possible to decrease the mounting area and height compared to the semiconductor device with the configuration of the prior art which are connected to the mother board by using outer leads, thus contributing to the reduction in the size and weight of the device.
Also because the die bond pads and the wire bond pads are directly connected to the mother board, heat dissipation from the semiconductor element is improved in comparison to the prior art configuration.
Thus, it becomes possible to secure stable operation even when high output power elements, which generate much heat are used for the semiconductor elements.
Also because the distance of connecting the mother board and the semiconductor element can be made shorter than that with the configuration of the prior art where connection with the mother board is made by using the outer leads, good high-frequency characteristics can be obtained even when a high-frequency element is used for the semiconductor element.
Also bonding area for bonding the semiconductor device onto the mother board with solder or the like by using the die bond pads and the wire bond pads is increased, thus making it possible to increase the bonding strength.
The present invention also provides a semiconductor device having at least two die bond pads.
The semiconductor element may also be mounted across a plurality of the die bond pads which are arranged in the longitudinal direction.
Die bond pads may also be disposed side by side with the die bond pads described above, with the semiconductor elements mounted across these die bond pads.
The present invention also provides a semiconductor device wherein a plurality of semiconductor elements which are disposed in longitudinal direction are molded with the same sealing resin.
As will be clear from the above description, according to the method of producing the semiconductor element of the present invention, because it is not necessary to prepare lead frames suitable for the individual semiconductor elements to be mounted thereon and the lead frame can be used in common, the production process can be simplified and the production cost can be reduced.
This method also makes it possible to use the lead frame in common by mounting the semiconductor element across a plurality of leads even when the semiconductor element of greater size is mounted.
Also because the lead frame with the semiconductor elements mounted thereon is sealed with the resin as a whole, it is not necessary to prepare different molding dies for various sizes of the semiconductor devices, thus the production process can be simplified and the production cost can be reduced.
Particularly because the lead frame with the semiconductor elements mounted thereon consecutively is cut off to make the semiconductor devices in this method, there is no part of the lead frame wasted, so that product yield per unit area of the lead frame is improved and the production cost can be reduced.
Also in the semiconductor device of the present invention, because only the front surface of the semiconductor device is sealed with the resin while the die bond pad and the wire bond pad formed on the back surface by cutting off the leads are exposed, the semiconductor device can be connected directly onto the mother board by using the back surface of the semiconductor device, thus making it possible to reduce the mounting area and height, thereby contributing to the reduction of size and weight.
Also because the die bond pad and the wire bond pad are connected directly to the mother board, heat dissipation from the semiconductor element can be improved, and the present invention can be applied to high-output power elements which generate much heat.
Also because the distance of connecting the mother board and the semiconductor element can be reduced, good high-frequency characteristic can be obtained when high-frequency element is used for the semiconductor element.
Also the bonding area for fastening the semiconductor device onto the mother board with solder or the like by using the die bond pads and the wire bond pads increases, thus making it possible to increase the bonding strength.